Stadium architect Kengo Kuma said on Wednesday there was "no need to worry"

Yoshiro Mori, Japan's former Prime Minister and president of the Tokyo 2020 delivers a speech during an unveiling event for the Tokyo 2020 Olympic and Paralympic games emblems at Tokyo Metropolitan Government Building in Tokyo July 24, 2015. REUTERS/Issei Kato/Files

The head of the Tokyo 2020 Olympic organising committee, Yoshiro Mori, blamed the Japanese sports minister on Friday for an embarrassing cauldron oversight at the new centrepiece stadium that has further marred Games preparations.

New venue plans adopted by the government in December after the initial one was scrapped following public outcry over spiralling costs made no mention of the location of the cauldron, where the Olympic flame burns throughout the Games.

Stadium architect Kengo Kuma said on Wednesday there was "no need to worry" and the cauldron would be placed safely after taking concerned questions about whether the $1.3 billion stadium would pass the Japanese Fire Service Act.

Mori, who has already fielded complaints about stadium construction delays and had to replace the Games logo after a plagiarism row, said main stadium operator, the Japan Sports Council (JSC), and Sports Minister Hiroshi Hase were culpable for the latest incident.

"The sports minister who supervises the JSC has to be held responsible," Mori was quoted as saying by Kyodo News on Friday.

"We've had nothing reported on the issue. It would make no sense not to think about the Olympic cauldron if the stadium was getting built for the Olympics."

Mori said he had spoken with International Olympic Committee (IOC) President Thomas Bach and been given consent to use the cauldron from the 1964 Games, the previous one hosted in Tokyo, for the 2020 edition.

The cauldron is currently located in Ishinomaki in Miyagi Prefecture, which was hit by the Fukushima earthquake and tsunami which struck five years ago.

Miyagi and Iwate Prefecture, also affected by the disaster which left 19,000 dead or missing after one of the worst earthquakes in history triggered a 10-meter high tsunami that crashed into the Fukushima Daiichi nuclear power station, have been given games to host at the 2019 Rugby World Cup.

Olympic Minister Toshiaki Endo said he had spoken with Mori and Bach about ensuring Fukushima could stage the opening rounds of the Olympic baseball and softball tournaments.

"I'd certainly like to host the sports at Fukushima Prefecture," Endo was quoted as saying by Kyodo on the anniversary of the Fukushima .

"At the moment, we have no events scheduled to take place in Fukushima, which has been most affected. We'll be working toward staging them there."